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754 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14
their upper surfaces. From a primary branch short lateral branches
extend to the zoids, entering them at the distal end. The autozoids
(feeding individuals) are usually straight, or only slightly curved. In
length they range from 0.47 to 0.55 mm, and in width they vary from
0.09 to 0.11 mm. Infrequently, an autozoid with a sharply pointed
rather than a bluntly rounded proximal end will be found. The tentacles are 12 in number, determined from serial sections. The reproductive zoid, the gonozoid, is usually as long as but may be slightly
shorter than the autozoid. Its proximal portion, extending below the
embryo chamber, is long, thin and slightly curved in the direction of the
embryo chamber. The embryo chamber is globular, giving the gonozoid
a "pot-bellied" appearance. The tentacle number of the gonozoid is 8,
but only in immature gonozoids will they be found, where the polypide
has not completely degenerated.
The specimens described in the original report by Silen were collected
from South Africa and the Cape of Good Hope, and there was one
"doubtful" specimen from Panama.
The specimens in the Hancock collection are from numerous localities
from San Pedro to La Jolla, southern California, all intertidal.
Penetrantia concharum Silen, 1946
Plate 80, fig. 9
Penetrantia concharum Silen, 1946:5.
Penetrantia concharum, Soule, 1950:360.
The zoids of the colonies are well spaced, without the crowding noted
in P. densa. The openings in the shell are well defined, reniform in
shape. The autozoids are straight, slender, with the proximal extremity
tapering to a point. The autozoids range in length from 0.46 to 0.54
mm, and in width from 0.08 to 0.10 mm. The tentacles number 10, as
determined from sections. The gonozoids are comparatively rare. The
proximal extremity of the gonozoids is straight and visibly thicker than
the gonozoid of P. densa.
Penetrantia concharum was found by Silen to occur in numerous
localities in Sweden and Norway.
The specimens in the Hancock collection are from several localities
ranging from San Pedro to La Jolla in southern California and southward to Rosarito, Lower California, Mexico (Hancock station 1597-
47). All are intertidal.

754 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14
their upper surfaces. From a primary branch short lateral branches
extend to the zoids, entering them at the distal end. The autozoids
(feeding individuals) are usually straight, or only slightly curved. In
length they range from 0.47 to 0.55 mm, and in width they vary from
0.09 to 0.11 mm. Infrequently, an autozoid with a sharply pointed
rather than a bluntly rounded proximal end will be found. The tentacles are 12 in number, determined from serial sections. The reproductive zoid, the gonozoid, is usually as long as but may be slightly
shorter than the autozoid. Its proximal portion, extending below the
embryo chamber, is long, thin and slightly curved in the direction of the
embryo chamber. The embryo chamber is globular, giving the gonozoid
a "pot-bellied" appearance. The tentacle number of the gonozoid is 8,
but only in immature gonozoids will they be found, where the polypide
has not completely degenerated.
The specimens described in the original report by Silen were collected
from South Africa and the Cape of Good Hope, and there was one
"doubtful" specimen from Panama.
The specimens in the Hancock collection are from numerous localities
from San Pedro to La Jolla, southern California, all intertidal.
Penetrantia concharum Silen, 1946
Plate 80, fig. 9
Penetrantia concharum Silen, 1946:5.
Penetrantia concharum, Soule, 1950:360.
The zoids of the colonies are well spaced, without the crowding noted
in P. densa. The openings in the shell are well defined, reniform in
shape. The autozoids are straight, slender, with the proximal extremity
tapering to a point. The autozoids range in length from 0.46 to 0.54
mm, and in width from 0.08 to 0.10 mm. The tentacles number 10, as
determined from sections. The gonozoids are comparatively rare. The
proximal extremity of the gonozoids is straight and visibly thicker than
the gonozoid of P. densa.
Penetrantia concharum was found by Silen to occur in numerous
localities in Sweden and Norway.
The specimens in the Hancock collection are from several localities
ranging from San Pedro to La Jolla in southern California and southward to Rosarito, Lower California, Mexico (Hancock station 1597-
47). All are intertidal.